The apparent viscosity of the hyaluronic acid was higher than that of the guar gum and carboxymethyl cellulose(CMC). The drinking water which added hyaluronic acid was obtained better evaluation than which added guar gam and CMC.In vitro digestion of hyaluronic acid were measured by article gastric juice porcine pancreatin rats intestinal mucosa and hyaluroniase ovine testes. Enzyme of arttical gastric juice porcine and rats intestinal mucosa digestion oh hyaluronic acid were not observed. The effects of hyaluronic acid were determined on the serum lipid levels and cecal microflora of rats. Male Wistar rats were fed on a control diet containing cholesterol (control diet) and on an experimental diet containing either 0.5% or 2.0% hyaluronic acid plus cholesterol for 60 days.The serum total cholesterol and free-cholesterol levels in the rats fed on the 0.6"% or 2.0% hyaluronic acid diet were significantly lower than the levels in the control diet, but the addition of hyaluronic acid to the diets induced no change to the concentration of HDL-cholesterol and triglyceride in the serum. More fecal bile acids were excreted by the hyaluronic acid diet groups than by the control diet group. A microflora examination revealed an increase in the counts of cecal Lactobacillus and Bifidobacterium during the administration of hyaluronic acid in the diet. These results suggest that the diets containing hyaluronic acid had a beneficial effect on the level of serum lipids and intestinal microflora.